Method of manufacturing a glass roll

ABSTRACT

A method of manufacturing a glass roll, includes: a forming step (S 1 ) of forming, while conveying a glass film, the glass film by a downdraw method; a temporary rolling step (S 3 ) of rolling the glass film while superposing a protective film on the glass film at a downstream end of a path of the conveying in the forming step (S 1 ), to thereby manufacture a source glass roll; and a main rolling step (S 4 ) of unrolling, while conveying the glass film to a downstream side, the glass film from the source glass roll, and then rerolling the glass film while superposing a protective film on the glass film at a downstream end of a path of the conveying, to thereby manufacture a glass roll. Higher tension in a rolling direction is applied to the glass film in the main rolling step (S 4 ) than in the temporary rolling step (S 3 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part application of international applicationPCT/JP2012/066252 filed Jun. 26, 2012 and U.S. patent application Ser.No. 13/038,747 filed Mar. 2, 2011, and claiming the priorities ofJapanese application 2011-146123 filed Jun. 30, 2011 and Japaneseapplication 2010-046111 filed Mar. 3, 2010.

TECHNICAL FIELD

The present invention relates to an improved technology of manufacturinga glass roll which is obtained by rolling a glass film formed by adowndraw method.

BACKGROUND ART

As is well known, flat panel displays (FPDs) have become mainstream asimage display devices in recent years, the FPDs being typified by aliquid crystal display, a plasma display, an organic light-emittingdiode (OLED) display, and the like. As substrates for those FPDs, glasssubstrates are used in order to secure various demanded properties suchas airtightness, flatness, heat resistance, translucency, and insulationproperty. Further, in view of reducing a weight, the glass substrates tobe used for the FPDs are currently becoming thinner. In particular, theFPDs such as an OLED display may be used under a state in which adisplay screen is bent, and hence thinning of the glass substrates hasbeen expected for the purpose of imparting flexibility to the glasssubstrates.

Further, there is a growing use of an OLED as a plane light source, suchas a light source for interior illumination, which emits only monochrome(for example, white) light, unlike a display that uses TFTs to blinklight of three fine primary colors. Further, when an OLED illuminationdevice includes a glass substrate having flexibility, a light-emittingsurface is freely deformable, which leads to an advantage in that theOLED illumination device is usable for a significantly wider range ofapplications. Therefore, from the viewpoint of ensuring sufficientflexibility, there is also promoted further thinning of the glasssubstrate to be used for the illumination device of this type.

In addition, operation of a touchscreen is performed by rubbing asurface of the touchscreen with human fingers and the like, and hence aglass substrate is often used in order to ensure fastness property ofthe surface of the touchscreen. Along with widespread use of mobiledevices equipped with a touchscreen of this type, thinning of the glasssubstrate for the touchscreen is required for reduction in weight of themobile devices.

In response to the above-mentioned demands for thinning, a glass filmthinned into a film shape (for example, having a thickness of 300 μm orless) has been developed. The glass film has appropriate flexibility,and hence is sometimes stored in a state of a so-called glass roll thatis formed by superposing a protective film on the glass film, androlling the glass film together with the protective film around a rollcore (for example, see Patent Literature 1). This reduces a storagespace for the glass film remarkably, and hence it is possible toincrease transportation efficiency. Further, with use of a roll-to-rollapparatus, various processes such as cutting and film formation can besequentially performed on a glass film that is unrolled from a glassroll situated on an upstream side, and hence it is possible toremarkably increase production efficiency.

CITATION LIST

-   Patent Literature 1: JP 2010-132350 A

SUMMARY OF INVENTION Technical Problems

By the way, the glass film is often formed by a downdraw method.Accordingly, in a case where the glass film is stored in a state of aglass roll, it is necessary that the glass film which is continuouslyformed from a forming body for carrying out the downdraw method berolled directly around the roll core.

However, in this case, when extreme tension (for example, tension ofabout 100 N per unit width (1 m) to the glass film) is applied to theglass film at the time of rolling, excessive tension is applied to apart of the glass film that is in a softened state near the formingbody. As a result, a thickness of the glass film may become unstable ora warpage or a wave may occur in the glass film. In some cases, theremay arise such a fatal problem that the glass film breaks below theforming body.

Therefore, it is actually difficult to roll the glass film whileapplying satisfactory tension to the glass film, and for example, therolled glass film moves afterward in a width direction thereof, with theresult that roll misalignment is more likely to occur. Further, unlessthe glass film is rolled while appropriate tension is applied to theglass film, the glass film in the state of the glass roll is separatedfrom the roll core, and hence an improper gap may be formed betweenlayered parts of the glass film. Further, when the roll misalignment orthe separation (radial gap) occurs in the glass film in this manner, theglass film is more likely to break, which leads to extremely troublesomehandling. In addition, in this case, the glass film is rolledirregularly, and hence an appearance of the glass roll is extremelydeteriorated, which may cause degradation in product value.

In view of the above-mentioned circumstances, the present invention hasa technical object to reduce as much as possible occurrence of rollmisalignment or separation in a glass film included in a glass roll whenthe glass film formed continuously by a downdraw method is stored in astate of the glass roll.

Solution to Problems

According to a first invention made to achieve the above-mentionedobject, there is provided a method of manufacturing a glass roll,comprising: a forming step of forming, while conveying a glass film to adownstream side, the glass film by a forming device for carrying out adowndraw method; a first rolling step of rolling the glass film whilesuperposing a first protective film on the glass film at a downstreamend of a path of the conveying in the forming step, to therebymanufacture a source glass roll; and a second rolling step of unrolling,while conveying the glass film to the downstream side, the glass filmfrom the source glass roll, and then rerolling the glass film whilesuperposing a second protective film on the glass film at a downstreamend of a path of the conveying, to thereby manufacture a glass roll,wherein tension in a rolling direction to be applied to the glass filmin the second rolling step is set higher than tension to be applied tothe glass film in the first rolling step.

With this method, the glass film rolled in the first rolling step isrerolled under a state in which higher tension is applied in the rollingdirection (direction of conveying the glass film) in the second rollingstep than in the first rolling step. Accordingly, in the first rollingstep in which the glass film formed by the forming device is rolleddirectly, it is unnecessary to roll the glass film while applyingexcessive tension to the glass film. In other words, in the firstrolling step, it is only necessary to apply tension to the glass filmwithin such a range as to prevent adverse effects such as anunreasonable fluctuation in thickness of the glass film formed by theforming device. As a result, even if roll misalignment or separationoccurs in the glass film, it is possible to straighten the rollmisalignment or the separation in the second rolling step. That is, inthe second rolling step, even if high tension is applied to the glassfilm, formation of the glass film is not adversely affected. Thus, whileapplying tension high enough to prevent the roll misalignment or theseparation from occurring in the glass film, it is possible to rerollthe glass film so as to manufacture the glass roll.

In the above-mentioned method, it is preferred that, in the firstrolling step, tension in the rolling direction to be applied to thefirst protective film be set higher than the tension in the rollingdirection to be applied to the glass film.

With this, without applying high tension directly to the glass film, itis possible to restrain movement of the glass film by the firstprotective film. That is, it is possible to obtain the same effect asthat in a case of applying tension directly to the glass film.Accordingly, it is possible to minimize the roll misalignment or theseparation of the glass film that occurs in the first rolling step.Further, the glass film in a state of the source glass roll is reliablyheld by the first protective film, and hence the following situation isless likely to arise: the glass film in the source glass roll is rolledextremely tightly when the glass film is unrolled from the source glassroll in the second rolling step. Note that, when the glass film isrolled tightly, friction is generated between the glass film and theprotective film, and hence micro flaws may be formed in a surface of theglass film.

In the above-mentioned method, in the second rolling step, the tensionin the rolling direction to be applied to the glass film may be sethigher than tension in the rolling direction to be applied to the secondprotective film.

With this, in the glass roll to be manufactured in the second rollingstep, that is, in the glass roll to be manufactured as a product, it ispossible to reliably prevent such a situation that tension applied tothe glass film itself causes the roll misalignment or the separation inthe glass film afterward. In other words, the glass film is notstraightened by being forcibly held by the second protective film, andhence extreme stress is less likely to act on the glass film. As aresult, a stable package state can be maintained.

In the above-mentioned method, it is preferred that, in the secondrolling step, the glass film be conveyed while only one surface of theglass film is contact-supported.

With this, another surface of the glass film is formed as a non-contactsurface. Accordingly, micro flaws resulting from conveyance are lesslikely to be formed in the surface of the glass film formed as thenon-contact surface. Therefore, in a case where a glass substrate forFPDs such as an OLED display is fabricated from the glass film, whenelements and wiring are formed on the non-contact surface side of theglass film, the micro flaws are less likely to cause poor formation ofthe elements and the wiring. Accordingly, it is possible to providehighly-reliable FPDs.

In the above-mentioned method, it is preferred that, in the secondrolling step, the glass film be rolled so that the contact-supportedsurface of the glass film is situated on an inner peripheral surfaceside of the glass roll.

With this, even if the micro flaws occur in the contact-supportedsurface of the glass film, the glass film is rolled so that thecontact-supported surface is situated on the inner peripheral surfaceside of the glass roll, and hence only compressive stress is applied tothe contact-supported surface. Therefore, even when the micro flawsoccur in the contact-supported surface, a force to propagate the microflaws is less likely to act. In other words, on the outer peripheralsurface side of the glass film on which the force to propagate the microflaws acts, a non-contact surface having substantially no micro flaws issituated, and hence breakage of the glass film can be reliably reduced.

In the above-mentioned method, in at least one of the first rolling stepand the second rolling step, the glass film may be rolled after beingcut by laser cutting into pieces each having a predetermined width.Here, the laser cutting comprises laser cleaving and laser fusing. Thelaser cleaving is a method of cutting the glass film in such a mannerthat an initial crack is propagated by utilizing thermal stress that isgenerated through expansion due to a heating action of laser and throughcontraction due to a cooling action of a refrigerant. On the other hand,the laser fusing is a cutting method of a jetting high pressure gas to aregion of glass that is heated by laser energy to be softened andmelted.

With this method, for example, in a case where the glass film is formedby an overflow downdraw method, it is possible to roll the glass filmafter cutting and removing an unavailable portion (ear portion) which isformed at each widthwise end portion of the glass film to have arelatively large thickness. Further, it is possible to roll the glassfilm after changing the glass film into pieces each having a desiredwidth. The pieces of the glass film are cut by laser cutting, and henceit is possible to obtain an advantage that micro cracks causing breakageare less likely to be formed in a cut end surface of the glass film.

In the above-mentioned method, it is preferred that the downdraw methodbe an overflow downdraw method.

With this, without subjecting the surface of the glass film to separateprocessing after formation of the glass film, excellent smoothness withlow surface roughness can be imparted to the surface of the glass film.

In the above-mentioned method, it is preferred that the glass film havea thickness of 1 μm or more and 300 μm or less.

With this, satisfactory flexibility can be imparted to the glass film,and hence it is possible to reduce such a situation that extreme stressis applied to the glass film when the glass film is rolled, which leadsto prevention of breakage of the glass film.

According to a second invention made to achieve the above-mentionedobject, there is provided a method of manufacturing a glass roll,comprising: forming a glass film by a downdraw method; and rolling theformed glass film while superposing the glass film on a protective film,wherein the glass film and the protective film are rolled while highertension in a rolling direction is applied to the protective film than tothe glass film.

With this method, without applying high tension in the rolling directionto the glass film, the glass film can be tightened by relatively hightension in the rolling direction applied to the protective film, andhence the glass roll free from loose rolling can be manufactured.Further, tension in the rolling direction is not applied to the glassfilm or the tension is low at the time of rolling the glass film.Accordingly, even in a case where the glass film is rolled after beingcurved along a substantially horizontal direction in a curved region, achange in curvature of the curved region can be prevented, and henceformation of the glass film is stabilized, with the result that theglass film free from warpage, waviness, and a change in thickness can berolled.

In the above-mentioned method, an unavailable portion (ear portion)formed at each widthwise end portion of the glass film may be cut by alaser cutting by the time the glass film is rolled. Here, the lasercutting comprises laser cleaving and laser fusing. The laser cleaving isa method of cutting the glass film in such a manner that an initialcrack is propagated by utilizing thermal stress that is generatedthrough expansion due to a heating action of laser and throughcontraction due to a cooling action of a refrigerant. On the other hand,the laser fusing is a cutting method of jetting a high pressure gas to aregion of glass that is heated by laser energy to be softened andmelted.

With this, without performing post-processing such as polishing, it ispossible to easily impart moderate smoothness to a cut surfaceconstituting each widthwise end surface of the glass film. Further,relatively high tension in the rolling direction is applied to theprotective sheet, and hence the end surface of the glass film and theprotective sheet are easily held in contact with each other. However,even in the case of contact, owing to the smoothed end surface of theglass film, the end surface does not bite into the protective sheet, andhence it is possible to satisfactorily maintain separability between theglass film and the protective sheet. Further, when rolling the glassfilm, small flaws are less likely to occur on the each end surface ofthe glass film. Thus, it is possible to reduce glass powder, which isgenerated due to chips resulting from the small flaws on the end surfaceof the glass film, and hence there is a great advantage in ensuringcleanness of the front and back surfaces of the glass film.

In the above-mentioned method, it is preferred that the glass film andthe protective film be rolled while the protective film is superposed onan outer peripheral surface side of the glass film so that theprotective film may be kept to form an outermost layer.

With this, the glass film can be easily tightened by the protectivefilm, and hence it is possible to reliably manufacture the glass rollfree from looseness.

In the above-mentioned method, it is preferred that the downdraw methodbe an overflow downdraw method.

With this, it is possible to form the glass film excellent in surfacesmoothness without performing additional processing after the forming,and hence it is possible to easily manufacture the glass roll excellentin surface accuracy.

According to a third invention made to achieve the above-mentionedobject, there is provided a glass roll, which is obtained by rolling aglass film formed by a downdraw method while superposing the glass filmon a protective film, wherein higher tension in a rolling direction isapplied to the protective film than to the glass film.

This configuration can provide a glass roll without looseness, which isobtained by rolling the glass film free from warpage, waviness, and achange in thickness.

In the above-mentioned configuration, it is preferred that the glassfilm have a thickness of 1 μm or more and 300 μm or less.

With this, it is possible to impart appropriate flexibility to the glassfilm. Accordingly, it is possible to reduce extreme stress to be appliedto the glass film when rolling the glass film, and to prevent the glassfilm from breaking.

In the above-mentioned configuration, it is preferred that eachwidthwise end surface of the glass film have an arithmetic averageroughness Ra of 0.1 μm or less.

With this, it is possible to impart appropriate smoothness to the eachwidthwise end surface of the glass film. Relatively high tension in therolling direction is applied to the protective sheet, and hence the endsurface of the glass film and the protective film are easily held incontact with each other. However, even in the case of contact, owing tothe smoothed end surface of the glass film, the end surface does notbite into the protective film, and hence it is possible tosatisfactorily maintain separability between the glass film and theprotective film.

In the above-mentioned configuration, it is preferred that theprotective film extend beyond both widthwise sides of the glass film.

With this, it is possible to protect the each widthwise end surface ofthe glass film with the protective film. Further, each widthwise end ofthe glass film is covered with the protective film, and hence it is alsopossible to prevent intrusion of foreign matters from an outside.

Advantageous Effects of Invention

According to the above-mentioned first invention, after the glass filmformed by a downdraw method is rolled in the first rolling step, therolled glass film is rerolled in the second rolling step while highertension is applied in the rolling direction in the second rolling stepthan in the first rolling step. Accordingly, even in a case where theglass film is formed continuously by a downdraw method, appropriatetension is applied to the glass film through the first rolling step andthe second rolling step, and hence it is possible to manufacture theglass roll in which the roll misalignment or the separation is lesslikely to occur.

Further, according to the above-mentioned second and third inventions,without applying high tension in the rolling direction to the glassfilm, the glass film can be tightened by relatively high tension in therolling direction that is applied to the protective film, and hence itis possible to manufacture the glass roll in which the roll misalignmentor the separation is less likely to occur.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A flow chart illustrating a method of manufacturing a glass rollaccording to an embodiment of the present invention.

FIG. 2 A diagram illustrating a state of implementation of a formingstep, a cutting step, and a temporary rolling step which are included inthe method of manufacturing a glass roll according to the embodiment ofthe present invention.

FIG. 3 A diagram illustrating a state of implementation of a mainrolling step which is included in the method of manufacturing a glassroll according to the embodiment of the present invention.

FIG. 4 A diagram illustrating another state of implementation of themain rolling step which is included in the method of manufacturing aglass roll according to the embodiment of the present invention.

FIG. 5 A diagram illustrating still another state of implementation ofthe main rolling step which is included in the method of manufacturing aglass roll according to the embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention are described withreference to the drawings.

FIG. 1 is a flow chart illustrating a method of manufacturing a glassroll according to a first embodiment of the present invention. Themethod of manufacturing a glass roll comprises a forming step S1, acutting step S2, a temporary rolling step (first rolling step) S3, and amain rolling step (second rolling step) S4.

In this embodiment, as illustrated in FIG. 2, the forming step S1 isperformed by a forming device 1 for carrying out an overflow downdrawmethod. The forming device 1 comprises a forming zone 2, an annealingzone 3, and a cooling zone 4 in the stated order from top to bottom.Note that, the forming device 1 may carry out another downdraw methodsuch as a slot downdraw method and a redraw method.

In the forming zone 2, molten glass Gm is fed to a forming body 5 havinga wedge-shaped cross-section, and the molten glass Gm overflowing from atop of the forming body 5 to both sides thereof is fused at a lower endportion of the forming body 5 so as to flow downward. In this manner, aplate-like glass film G is formed from the molten glass Gm. The glassfilm G gradually increases in viscosity as the glass film G movesdownward. After its viscosity reaches viscosity high enough to becapable of keeping the shape, strain of the glass film G is removed inthe annealing zone 3, and further, the glass film G is cooled to nearroom temperature in the cooling zone 4.

In the annealing zone 3 and the cooling zone 4, at a plurality of pointsranging from an upstream side to a downstream side of a conveying pathfor the glass film G, a roller group 6 comprising pairs of rollers isarranged, for guiding both widthwise end portions of the glass film Gdownward. Note that, in this embodiment, rollers, which are arranged inan uppermost portion of the forming zone 2 within the forming device 1,function as cooling rollers for cooling both the widthwise end portionsof the glass film G, and also function as driving rollers for drawingthe glass film G downward. On the other hand, residual rollers arrangedwithin the forming device 1 function as idle rollers, tension rollers,and the like, for guiding the glass film G downward.

The glass film G formed in this forming step S1 is a long film having athickness of from 1 to 600 μm (preferably, 1 to 300 μm, and morepreferably, 10 to 200 μm). The glass film G is employed for, forexample, a flat panel display (FPD) such as a liquid crystal display, aplasma display, and an OLED display, a glass substrate for a device suchas a solar cell, a lithium ion battery, a digital signage, a touchpanel, and an electronic paper display, a cover glass for an OLEDlighting, a glass container for medical supplies, a window glass, and alightweight laminated window glass.

Further, a width of the glass film G is preferably 100 mm or more, morepreferably 300 mm or more, and still more preferably 500 mm or more.Note that, the glass film G is used for a wide variety of devicesincluding a small-screen display such as a mobile phone with a smallsize and a large-screen display such as a television set with a largesize. Thus it is preferred that the width of the glass film G be finallyselected as appropriate depending on a size of a substrate of a deviceto be used.

Further, as a glass composition of the glass film G, there can be usedvarious glass compositions of silicate glass and the like, such assilica glass and borosilicate glass. However, it is preferred to usenon-alkali glass. The reason is as follows. When the glass film Gcontains an alkali component, a so-called too-abundant soda phenomenonoccurs so that the glass film is structurally weathered. When the glassfilm G is curved, there is a risk in that the glass film is prone tobreak from a portion that is structurally weathered over time. Notethat, the non-alkali glass herein comprises glass that does notsubstantially contain an alkali component, specifically, glasscontaining an alkali metal oxide of 1,000 ppm or less (preferably, of500 ppm or less, and more preferably, of 300 ppm or less). Examples ofglass satisfying this condition include OA-10G manufactured by NipponElectric Glass Co., Ltd.

Further, after the glass film G formed in the forming step S1 asdescribed above is curved in a substantially horizontal direction by aposture changing roller group 7 which comprises a plurality of rollersfor supporting the glass film G from below at positions below theforming device 1, the glass film G is conveyed to the cutting step S2while keeping its posture. Note that, the posture changing roller group7 may be omitted as appropriate.

In the cutting step S2, an unavailable portion (ear portion) Gx formedat each widthwise end portion of the glass film G in the forming step S1is cut and removed by a cutting device 8. The unavailable portion Gx isrelatively thicker than an available portion Ga formed at a widthwisecenter portion of the glass film G.

Specifically, the cutting device 8 carries out laser cleaving, andcomprises: conveying means 9 for conveying the glass film G, which isformed continuously by the forming device 1, to the downstream sidewhile keeping the glass film G in a substantially horizontal posture;locally heating means 10 for locally heating the glass film G, which isplaced on the conveying means 9, through application of a laser beam Lfrom a front surface side of the glass film G; and cooling means 11 forjetting cooling water W from the front surface side of the glass film Gonto a heated region heated by the locally heating means 10. When theglass film G is cut by laser cleaving in this manner, without performingpost-processing such as polishing, appropriate smoothness can be easilyimparted to a cut surface which forms each widthwise end surface of theglass film G. Accordingly, the end surface of the glass film G does notbite into a protective film F1, and hence there is an advantage that itis possible to satisfactorily keep separation property between the glassfilm G and the protective film F1. There is also another advantage thata chip resulting from micro flaws is less likely to occur in each endsurface of the glass film G when the glass film G is rolled. Here, inview of attaining the above-mentioned advantages more reliably, anarithmetic average roughness Ra of each widthwise end surface of theglass film G is preferably 0.1 μm or less, and more preferably 0.05 μmor less.

In this embodiment, a carbon dioxide laser is used as the locallyheating means 10, but alternatively, there may be used means capable ofperforming another type of localized heating such as heating with aheating wire or hot air blast. Further, the cooling means 11 jets thecooling water W as a refrigerant using an air pressure or the like. Inthis context, the refrigerant may include a cooling liquid other thanthe cooling water, a gas such as air or an inert gas, a mixture of a gasand a liquid, a mixture of a solid such as solid carbon dioxide or iceand the gas and/or the liquid, or the like. Note that, the cuttingdevice 8 may carry out breaking and cutting along a scribe line using adiamond cutter, or carry out laser fusing.

The conveying means 9 conveys the glass film G to the downstream side,and thus prior to a region to be cooled by the cooling means 11, aregion to be heated by the locally heating means 10 is subjected toscanning performed from one end portion side of the glass film G along apreset cleaving line (boundary portion between the available portion Gaand the unavailable portion Gx) extending in a longitudinal direction ofthe glass film G. With this, thermal stress is generated throughexpansion due to a heating action and through contraction due to acooling action of a refrigerant, and an initial crack (not shown), whichis previously formed in a leading end portion of the preset cleavingline, propagates along the preset cleaving line. In this manner, theglass film G is subjected to full-body cleaving continuously.

The cut unavailable portion Gx of the glass film G is bent downward tobe separated from the available portion Ga, and then is discarded. Onthe other hand, the available portion Ga of the glass film G is conveyedto the temporary rolling step S3.

In the temporary rolling step S3, in order that the protective film F1may be kept to form an outermost layer, the glass film G (specifically,available portion Ga) is rolled by a predetermined length around a rollcore 13 while the protective film F1 unrolled from a protective roll 12is superposed on an outer peripheral surface side of the glass film G,and then the glass film G and the protective film F1 are cut by acutting device (not shown) in a width direction thereof. Thus, a sourceglass roll 14 is manufactured. At this time, when tension is excessivelyapplied to the glass film G, excessive tension is applied to a part ofthe glass film G that is in a softened state near the forming body 5. Asa result, a thickness of the glass film G may become unstable, or insome cases, there may arise such a fatal problem that the glass film Gbreaks below the forming body 5. Accordingly, in the temporary rollingstep S3, while tension (for example, tension of from 0 to less than 20 Nper unit width (1 m) to the glass film G) is applied to the glass film Galong a rolling direction within such a range as to prevent adverseeffects on formation of the glass film G, the glass film G is rolledaround the roll core 13. Here, in the temporary rolling step S3, it isnot necessary to actively apply tension to the glass film G, and hencethere may be applied only minimum tension that acts spontaneously whenthe glass film G is rolled.

Further, in this embodiment, in the temporary rolling step S3, highertension in the rolling direction is applied to the protective film F1than to the glass film G. Specifically, for example, tension of from 0.8to 400 N per unit width (1 m) is applied to the protective film F1. Thetension to be applied to the protective film F1 is applied, for example,through setting a difference in rotation speed between the source glassroll 14 and the protective roll 12, or through interposing a tensionroller 15 as illustrated in the drawing between the source glass roll 14and the protective roll 12. With this, without applying high tensiondirectly to the glass film G, it is possible to restrain movement of theglass film G by the protective film F1. That is, it is possible toobtain the same effect as that in a case of applying tension directly tothe glass film G. Accordingly, it is possible to minimize rollmisalignment or separation of the glass film G that occurs in thetemporary rolling step S3. Further, the glass film G in a state of thesource glass roll 14 is reliably held by the protective film F1, andhence the following situation is less likely to arise: the glass film Gin the source glass roll 14 is rolled extremely tightly when the glassfilm G is unrolled from the source glass roll 14 in the main rollingstep S4 described below.

It is preferred that the protective film F1 for the source glass roll 14have a thickness of from 20 to 1,000 μm (more preferably, from 25 to 500μm). Further, it is preferred that the protective film F1 have a widthlarger than a width of the available portion Ga of the glass film G inorder to protect both widthwise end surfaces of the glass film G fromvarious contacts. That is, it is preferred that the protective film F1extend beyond both widthwise sides of the available portion Ga of theglass film G.

Further, by the time the temporary rolling step S3 is carried out, thetemperature of the glass film G sometimes reaches 50° C. or more, andhence it is preferred that the protective film F1 be not transformed,for example, not softened at a temperature of around 100° C.

It is preferred that an elastic film be used for the protective film F1.With this, it is possible to produce the source glass roll 14 free fromlooseness while applying appropriate tension in the rolling direction tothe protective film F1. It is preferred that a tensile elastic modulusof the protective film F1 be from 1 to 5 GPa.

It is preferred that conductivity be imparted to the protective film F1.With this, when the glass film G is taken out of the source glass roll14, peeling electrification is less likely to occur between the glassfilm G and the protective film F1, therefore there may be an advantagethat the protective film F1 can be easily peeled off from the glass filmG. Examples of a method of imparting conductivity to the protective filmF1 includes, for example, in a case where the protective film F1 is madeof a resin, adding a component for imparting the conductivity, such aspolyethylene glycol, into the protective film F1, and in a case wherethe protective film F1 is made of inserting paper, adding conductivefiber into the inserting paper. Further, it is possible to impart theconductivity into the protective film F1 also by laminating a conductivelayer, such as an indium-tin-oxide (ITO) film, on a surface of theprotective film F1.

Specifically, as the protective film F1, there can be used a resin film,for example, an organic resin film (synthetic resin film) such as anionomer film, a polyethylene film, a polypropylene film, a polyvinylchloride film, a polyvinylidene chloride film, a polyvinyl alcohol film,a polyester film, a polycarbonate film, a polystyrene film, apolyacrylonitrile film, an ethylene vinyl acetate copolymer film, anethylene-vinyl alcohol copolymer film, an ethylene-methacrylatecopolymer film, a polyamide film, a polyimide film, and cellophane.Further, in view of ensuring cushioning performance, as the protectivefilm F1, there can be used a foamed resin film such as an expandedpolyethylene resin film, and a composite material obtained by laminatingthe foamed resin film on the above-mentioned resin films. In addition,in the above-mentioned resin films, there may be dispersed a lubricantsuch as silica, which yields a satisfactory degree of slip on the glassfilm G. With this, slipping property of the protective film F1 canabsorb a difference in lengths to be rolled between the glass film G andthe protective film F1, which results from a slight difference indiameters to be rolled between the glass film G and the protective filmF1. Note that, the same applies to a protective film F2 for a glass roll16 described below.

Note that, regarding the above-mentioned matters relating to theprotective film F1, the same applies to the protective film F2 for theglass roll 16 described below.

The source glass roll 14 manufactured in the temporary rolling step S3as described above is conveyed to the main rolling step S4, and then isrerolled.

In the main rolling step S4, as illustrated in FIG. 3, with use of aroll-to-roll apparatus, the glass film G (specifically, availableportion Ga) unrolled from the source glass roll 14 is rerolled, and thusthe glass roll 16 as a product is manufactured.

Specifically, in this embodiment, after the glass film G unrolled fromthe source glass roll 14 at an unrolling position P1 is guided on aroundabout route in a substantially circumferential manner by a rollergroup 17 comprising a plurality of rollers, the glass film G is rerolledaround a roll core 18 at a rolling position P2. Thus, the glass roll 16is manufactured. When the glass film G is guided in this manner,appropriate tension is easily applied to the glass film G also betweenthe respective rollers of the roller group 17.

At this time, at the unrolling position P1, the protective film F1 ispeeled off from the glass film G, and the peeled-off protective film F1is rolled into a protective roll 19. On the other hand, at the rollingposition P2, in order that the protective film F2 may be kept to form anoutermost layer, the glass film G is rolled around the roll core 18while the protective film F2 unrolled from another protective roll 20 issuperposed on the outer peripheral surface side of the glass film G.Then, after the glass film G is rolled by a predetermined length aroundthe roll core 18 while the protective film F2 is superposed on the glassfilm G, the protective film F2 (or the glass film G and the protectivefilm F2) is cut by the cutting device (not shown) in the width directionthereof. Thus, the glass roll 16 is manufactured. In this embodiment,the protective film F2 is the same type as the protective film F1 usedin the temporary rolling step S3.

Further, in the main rolling step S4, as illustrated in FIG. 1, tension“b” in the rolling direction to be applied to the glass film G is sethigher than tension “a” to be applied to the glass film G in thetemporary rolling step S3. Specifically, for example, tension of from 10to 500 N per unit width (1 m) is applied to the glass film G. Thetension to be applied to the glass film G is applied, for example,through setting a difference in rotation speed between the source glassroll 14 and the glass roll 16. Thus, even if roll misalignment orseparation occurs in the glass film G which is included in the sourceglass roll 14 manufactured in the temporary rolling step S3, it ispossible to apply satisfactory tension to the glass film G in the mainrolling step S4, and to reroll the glass film G while straightening theroll misalignment or the like.

Note that, in the main rolling step S4, higher tension in the rollingdirection may be applied to the glass film G than to the protective filmF2. Specifically, for example, it is preferred that tension of from 0.8to 400 N per unit width (1 m) be applied to the protective film F2. Thetension to be applied to the protective film F2 is applied, for example,through setting a difference in rotation speed between the glass roll 16and the protective roll 20, or through interposing a tension roller 21as illustrated in the drawings between the glass roll 16 and theprotective roll 20. In this case, a magnitude relation between thetension in the rolling direction to be applied to the protective film F2in the main rolling step S4 and the tension in the rolling direction tobe applied to the protective film F1 in the temporary rolling step S3 isnot particularly limited to the above. It is possible to set themagnitude relation as appropriate in consideration of various conditions(tension to the protective film F1<tension to the protective film F2,tension to the protective film F1=tension to the protective film F2,tension to the protective film F1>tension to the protective film F2).

Further, in the main rolling step S4, as illustrated in FIG. 3, theglass film G is conveyed while only one surface of the glass film G iscontact-supported, and the glass film G is rolled so that thecontact-supported surface is situated on an inner peripheral surfaceside of the glass roll 16. Thus, even when the micro flaws occur in thecontact-supported surface of the glass film G, the glass film G isrolled so that the contact-supported surface is situated on the innerperipheral surface side of the glass roll 16. In the glass roll 16, onlycompressive stress is applied to the inner peripheral surface of theglass film G. Accordingly, even when the micro flaws occur in thecontact-supported surface, a force to propagate the micro flaws is lesslikely to act. In other words, on the outer peripheral surface of theglass film G on which the force to propagate the micro flaws acts, anon-contact surface having substantially no micro flaws is situated, andhence breakage of the glass film G can be reliably reduced. Note that,in this embodiment, also in the temporary rolling step S3, only onesurface of the glass film G is contact-supported, and thecontact-supported surface of the glass film G is set to the same side asthe contact-supported surface of the glass film G supported in the mainrolling step S4.

Note that, the present invention is not limited to the above-mentionedfirst embodiment, and can be implemented in various modes. For example,as illustrated in FIG. 4, also in the main rolling step S4, the cuttingstep may be carried out. Specifically, the glass film G (specifically,available portion Ga) unrolled from the source glass roll 14 is cut inthe width direction thereof to be divided into a plurality of (two inthe illustrated example) glass films G each having a desired width.Then, each of the glass films G is rolled around the roll core 18 whilesuperposing the protective film F2 on each of the glass films G. In thismanner, a plurality of glass rolls 16 may be manufactured at the sametime.

Further, in the above-mentioned embodiment, description is made of acase where a surface of the glass film G situated on the innerperipheral surface side in a state of the source glass roll 14 isconveyed as the contact-supported surface of the glass film G. However,as illustrated in FIG. 4, a surface of the glass film G situated on theouter peripheral surface side in the state of the source glass roll 14may be conveyed as the contact-supported surface of the glass film G.Further, in the above-mentioned embodiment, description is made of acase where the glass film G is rolled so that the contact-supportedsurface is situated on the inner peripheral surface side of the glassroll 16. However, the glass film G may be rolled so that thecontact-supported surface is situated on the outer peripheral surfaceside of the glass roll 16.

In addition, in the above-mentioned embodiment, description is made of acase where the glass film G unrolled from the source glass roll 14 isrolled in the main rolling step S4 after being guided on the roundaboutroute in the substantially circumferential manner. However, asillustrated in FIG. 5, the glass film G unrolled from the source glassroll 14 may be rolled after being guided in a straight manner.

Further, in the above-mentioned embodiment, description is made of acase where the main rolling step S4 is carried out only one time afterthe temporary rolling step S3. However, after the main rolling step S4,a step of further rerolling the glass film G may be carried out one or aplurality of times.

Next, description is made of a method of manufacturing a glass rollaccording to a second embodiment of the present invention. Note that,the second embodiment can be implemented in the same mode as thatillustrated in FIG. 1, but is different from the first embodiment inthat the temporary rolling step S3 is carried out as a main rolling stepof manufacturing a glass roll as an end product.

Specifically, in the second embodiment, as illustrated in FIG. 1, theglass film G is formed by a downdraw method, and the protective film F1is superposed on the outer peripheral side of the formed glass film G.Then, while higher tension in the rolling direction is applied to theprotective film F1 than to the glass film G, the protective film F1 andthe glass film G are rolled. In this manner, a glass roll as an endproduct is manufactured. Further, while the glass roll thus manufacturedremains rolled, higher tension in the rolling direction is applied tothe protective film F1 than to the glass film G.

Here, tension to be applied to the protective film F1 and tension to beapplied to the glass film G are the same as the tension described in thetemporary rolling step S3 described in the first embodiment (forexample, tension of from 0 to less than 20 N per unit width (1 m) to theglass film G, and tension of from 0.8 to 400 N per unit width (1 m) tothe protective film F1).

INDUSTRIAL APPLICABILITY

The present invention can be preferably used for a glass substrate usedfor a flat panel display, such as a liquid crystal display or an OLEDdisplay, for a glass substrate used for a device such as a solar cell,and for cover glass for an OLED lighting.

REFERENCE SIGNS LIST

-   -   1 forming device    -   2 forming zone    -   3 annealing zone    -   4 cooling zone    -   5 forming body    -   7 posture changing roller group    -   8 cutting device    -   9 conveying means    -   10 locally heating means    -   11 cooling means    -   14 source glass roll    -   16 glass roll    -   F1, F2 protective film    -   G glass film

1. A method of manufacturing a glass roll, comprising: a forming step offorming, while conveying a glass film to a downstream side, the glassfilm by a forming device for carrying out a downdraw method; a firstrolling step of rolling the glass film while superposing a firstprotective film on the glass film at a downstream end of a path of theconveying in the forming step, to thereby manufacture a source glassroll; and a second rolling step of unrolling, while conveying the glassfilm to the downstream side, the glass film from the source glass roll,and then rerolling the glass film while superposing a second protectivefilm on the glass film at a downstream end of a path of the conveying inthe second rolling step, to thereby manufacture a glass roll, whereintension in a rolling direction to be applied to the glass film in thesecond rolling step is set higher than tension to be applied to theglass film in the first rolling step.
 2. The method of manufacturing aglass roll according to claim 1, wherein, in the first rolling step,tension in the rolling direction to be applied to the first protectivefilm is set higher than the tension in the rolling direction to beapplied to the glass film.
 3. The method of manufacturing a glass rollaccording to claim 1, wherein, in the second rolling step, the tensionin the rolling direction to be applied to the glass film is set higherthan tension in the rolling direction to be applied to the secondprotective film.
 4. The method of manufacturing a glass roll accordingto claim 1, wherein, in the second rolling step, the glass film isconveyed while only one surface of the glass film is contact-supported.5. The method of manufacturing a glass roll according to claim 4,wherein, in the second rolling step, the glass film is rolled so thatthe contact-supported surface of the glass film is situated on an innerperipheral surface side of the glass roll.
 6. The method ofmanufacturing a glass roll according to claim 1, wherein, in at leastone of the first rolling step and the second rolling step, the glassfilm is rolled after being cut by laser cutting into pieces each havinga predetermined width.
 7. The method of manufacturing a glass rollaccording to claim 1, wherein the downdraw method comprises an overflowdowndraw method.
 8. The method of manufacturing a glass roll accordingto claim 1, wherein the glass film has a thickness of 1 μm or more and300 μm or less.
 9. A method of manufacturing a glass roll, comprising:forming a glass film by a downdraw method; and rolling the formed glassfilm while superposing the glass film on a protective film, wherein theglass film and the protective film are rolled while higher tension in arolling direction is applied to the protective film than to the glassfilm.
 10. The method of manufacturing a glass roll according to claim 9,wherein an unavailable portion formed at each widthwise end portion ofthe glass film is cut by laser cutting by the time the glass film isrolled.
 11. The method of manufacturing a glass roll according to claim9, wherein the glass film and the protective film are rolled while theprotective film is superposed on an outer peripheral surface side of theglass film so that the protective film is kept to form an outermostlayer.
 12. The method of manufacturing a glass roll according to claim9, wherein the downdraw method comprises an overflow downdraw method.13. A glass roll, which is obtained by rolling a glass film formed by adowndraw method while superposing the glass film on a protective film,wherein higher tension in a rolling direction is applied to theprotective film than to the glass film.
 14. The glass roll according toclaim 13, wherein the glass film has a thickness of 1 μm or more and 300μm or less.
 15. The glass roll according to claim 13, wherein eachwidthwise end surface of the glass film has an arithmetic averageroughness Ra of 0.1 μm or less.
 16. The glass roll according to claim13, wherein the protective film extends beyond both widthwise sides ofthe glass film.
 17. The method of manufacturing a glass roll accordingto claim 2, wherein, in the second rolling step, the tension in therolling direction to be applied to the glass film is set higher thantension in the rolling direction to be applied to the second protectivefilm.
 18. The method of manufacturing a glass roll according to claim 2,wherein, in the second rolling step, the glass film is conveyed whileonly one surface of the glass film is contact-supported.
 19. The methodof manufacturing a glass roll according to claim 18, wherein, in thesecond rolling step, the glass film is rolled so that thecontact-supported surface of the glass film is situated on an innerperipheral surface side of the glass roll.
 20. The method ofmanufacturing a glass roll according to claim 2, wherein, in at leastone of the first rolling step and the second rolling step, the glassfilm is rolled after being cut by laser cutting into pieces each havinga predetermined width.